Presently known apparati for restraining and removing dies in a punch press operation utilize a fixed-width restraining fixture and a die carriage which transports the die into and out of the restraining fixture. It also commonly utilizes a series of rack and pinion drive shafts, shear pins, a drive motor clutch, and a carriage, in addition to the restraining fixture necessary to hold the die while compaction takes place. The die will expand under the heavy pressure applied during compaction. However, the restraining fixture restrains the die, leaving it wedged in place when compaction is completed and the upper ram returns to its home position. Removing the die from the restraining fixture is then accomplished by using the die carriage. The lateral forces exerted against the fixed-width restraining fixture are extreme, and it requires high torque to release the die from the restraining fixture and propel it to the next work station. Breakdowns are frequent and often difficult to repair. In addition, the die assemblies weighing as much as 75-85 pounds must be physically pushed and moved from one location to another. These problems are all greatly exacerbated when working with highly toxic materials requiring the use of a glove box to isolate the operator from the workpiece.
U.S. Pat. No. 4,810,458 to Oshima et al. is representative of many patents wherein a floating air cushion or the like is used to support a workpiece. Oshima discloses a ceramic body which is continually extruded through a die of an extruder and is supported by a porous support, in a slightly floating state, by air pressure provided through pores of the support. U.S. Pat. Nos. 4,828,769 and 4,900,242, both to Maus et al, each disclose an apparatus for injection molding of articles, including a movable platen assembly. However, none of the known art solves the problems of restraining the die without binding, and of moving the die without elaborate machinery and heavy force requirements.
It is thus desirable to provide an apparatus which allows for ease of removal of a die after the completion of the compaction phase, while nonetheless still providing firm support for the die during the compaction phase. In addition, it is desirable to provide an apparatus which allows a die to be easily moved with minimal power and mechanical aid from one work station to the next in punch press operations. It is particularly important to provide apparatus allowing for these advantages when working with highly toxic materials requiring the use of a glove box, and where a high degree of automation may be desired.